The huge difference between Paid and free Advertising is you are trading money for time. If you have the money to do paid advertising I would highly reccomend the S-Builder Co=op
If you cant afford a whole S-builder co-op unit ask your upload about former a team co-op where you can purchase a 1/2 or 1/4 of a unit
You can learn about Free Advertising directly from SFI in Internert Marketing Lessons 23 and 24.